Method and apparatus for transmitting indication in wireless communication system

ABSTRACT

A method and apparatus for performing a transport network layer (TNL) address discovery procedure in a wireless communication system is provided. A first eNodeB (eNB) transmits at least one of a TNL address of the first eNB and a TNL address of an X2-gateway (GW), and a source eNB identifier (ID). The eNB may further transmit an indication of X2 setup which indicates whether a direct X2 interface between the first eNB and a second eNB or an indirect X2 interface going through the X2-GW is to be set up.

TECHNICAL FIELD

The present invention relates to wireless communications, and moreparticularly, to a method and apparatus for transmitting an indicationin a wireless communication system.

BACKGROUND ART

Universal mobile telecommunications system (UMTS) is a 3rd generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3GPP LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

FIG. 1 shows network structure of an evolved universal mobiletelecommunication system (E-UMTS). The E-UMTS may be also referred to asan LTE system. The communication network is widely deployed to provide avariety of communication services such as voice over Internet protocol(VoIP) through IMS and packet data.

As shown in FIG. 1, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an evolved packet core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNB) 20, and a plurality of user equipment (UE) 10 may belocated in one cell. One or more EUTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways (S-GW) 30 may bepositioned at the end of the network and connected to an externalnetwork.

As used herein, “downlink” refers to communication from the eNB 20 tothe UE 10, and “uplink” refers to communication from the UE 10 to theeNB 20. The UE 10 refers to communication equipment carried by a userand may be also referred to as a mobile station (MS), a user terminal(UT), a subscriber station (SS) or a wireless device.

The eNB 20 provides end points of a user plane and a control plane tothe UE 10. The MME/S-GW 30 provides an end point of a session andmobility management function for the UE 10. The eNB and MME/S-GW may beconnected via an S1 interface.

The eNB 20 is generally a fixed station that communicates with the UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNBs20.

The MME provides various functions including non-access stratum (NAS)signaling to the eNBs 20, NAS signaling security, access stratum (AS)security control, inter core network (CN) node signaling for mobilitybetween 3GPP access networks, idle mode UE reachability (includingcontrol and execution of paging retransmission), tracking area listmanagement (for UE in idle and active mode), packet data network (PDN)GW and serving GW selection, MME selection for handovers with MMEchange, serving GPRS support node (SGSN) selection for handovers to 2Gor 3G 3GPP access networks, roaming, authentication, bearer managementfunctions including dedicated bearer establishment, support for publicwarning system (PWS) (which includes earthquake and tsunami warningsystem (ETWS) and commercial mobile alert system (CMAS)) messagetransmission. The S-GW host provides assorted functions includingper-user based packet filtering (by e.g., deep packet inspection),lawful interception, UE IP address allocation, transport level packetmarking in the downlink, UL and DL service level charging, gating andrate enforcement, DL rate enforcement based on APN-AMBR. For clarity,the MME/S-GW 30 will be referred to herein simply as a “gateway,” but itis understood that this entity includes both the MME and the SAEgateway.

A plurality of nodes may be connected between the eNB 20 and the gateway30 via the S1 interface. The eNBs 20 may be connected to each other viaan X2 interface and neighboring eNBs may have a meshed network structurethat has the X2 interface.

FIG. 2 shows architecture of a typical E-UTRAN and a typical EPC.

As shown, the eNB 20 may perform functions of selection for the gateway30, routing toward the gateway during a radio resource control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of broadcast channel (BCH) information, dynamicallocation of resources to the UEs 10 in both uplink and downlink,configuration and provisioning of eNB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, the gateway 30 mayperform functions of paging origination, LTE_IDLE state management,ciphering of the user plane, SAE bearer control, and ciphering andintegrity protection of NAS signaling.

FIG. 3 shows a user-plane protocol and a control-plane protocol stackfor an E-UMTS.

FIG. 3( a) is block diagram depicting the user-plane protocol, and FIG.3( b) is block diagram depicting the control-plane protocol. As shown,the protocol layers may be divided into a first layer (L1), a secondlayer (L2) and a third layer (L3) based upon the three lower layers ofan open system interconnection (OSI) standard model that is well knownin the art of communication systems.

The physical layer, the L1, provides an information transmission serviceto an upper layer by using a physical channel. The physical layer isconnected with a medium access control (MAC) layer located at a higherlevel through a transport channel, and data between the MAC layer andthe physical layer is transferred via the transport channel. Betweendifferent physical layers, namely, between physical layers of atransmission side and a reception side, data is transferred via thephysical channel.

The MAC layer of the L2 provides services to a radio link control (RLC)layer (which is a higher layer) via a logical channel. The RLC layer ofthe L2 supports the transmission of data with reliability. It should benoted that the RLC layer shown in FIGS. 3( a) and 3(b) is depictedbecause if the RLC functions are implemented in and performed by the MAClayer, the RLC layer itself is not required. A packet data convergenceprotocol (PDCP) layer of the L2 performs a header compression functionthat reduces unnecessary control information such that data beingtransmitted by employing IP packets, such as IPv4 or IPv6, can beefficiently sent over a radio (wireless) interface that has a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the lowest portion ofthe L3 is only defined in the control plane and controls logicalchannels, transport channels and the physical channels in relation tothe configuration, reconfiguration, and release of the radio bearers(RBs). Here, the RB signifies a service provided by the L2 for datatransmission between the terminal and the UTRAN.

As shown in FIG. 3( a), the RLC and MAC layers (terminated in the eNB 20on the network side) may perform functions such as scheduling, automaticrepeat request (ARQ), and hybrid automatic repeat request (HARM). ThePDCP layer (terminated in the eNB 20 on the network side) may performthe user plane functions such as header compression, integrityprotection, and ciphering.

As shown in FIG. 3( b), the RLC and MAC layers (terminated in the eNodeB20 on the network side) perform the same functions for the controlplane. As shown, the RRC layer (terminated in the eNB 20 on the networkside) may perform functions such as broadcasting, paging, RRC connectionmanagement, RB control, mobility functions, and UE measurement reportingand controlling. The NAS control protocol (terminated in the MME ofgateway 30 on the network side) may perform functions such as a SAEbearer management, authentication, LTE_IDLE mobility handling, pagingorigination in LTE_IDLE, and security control for the signaling betweenthe gateway and UE the 10.

The RRC state may be divided into two different states such as aRRC_IDLE and a RRC_CONNECTED. In RRC_IDLE state, the UE 10 may receivebroadcasts of system information and paging information while the UEspecifies a discontinuous reception (DRX) configured by NAS, and the UEhas been allocated an identification (ID) which uniquely identifies theUE in a tracking area and may perform PLMN selection and cellre-selection. Also, in RRC_IDLE state, no RRC context is stored in theeNB.

In RRC_CONNECTED state, the UE 10 has an E-UTRAN RRC connection and acontext in the E-UTRAN, such that transmitting and/or receiving datato/from the network (eNB) becomes possible. Also, the UE 10 can reportchannel quality information and feedback information to the eNB.

In RRC_CONNECTED state, the E-UTRAN knows the cell to which the UE 10belongs. Therefore, the network can transmit and/or receive data to/fromthe UE 10, the network can control mobility (handover and inter-radioaccess technologies (RAT) cell change order to GSM EDGE radio accessnetwork (GERAN) with network assisted cell change (NACC)) of the UE, andthe network can perform cell measurements for a neighboring cell.

In RRC_IDLE state, the UE 10 specifies the paging DRX cycle.Specifically, the UE 10 monitors a paging signal at a specific pagingoccasion of every UE specific paging DRX cycle.

The paging occasion is a time interval during which a paging signal istransmitted. The UE 10 has its own paging occasion.

A paging message is transmitted over all cells belonging to the sametracking area. If the UE 10 moves from one tracking area to anothertracking area, the UE will send a tracking area update message to thenetwork to update its location.

FIG. 4 shows a structure of a physical channel.

The physical channel transfers signaling and data between layer L1 ofthe UE and eNB. As shown in FIG. 4, the physical channel transfers thesignaling and data with a radio resource, which consists of one or moresub-carriers in frequency and one more symbols in time.

One sub-frame, which is 1 ms in length, consists of several symbols. Theparticular symbol(s) of the sub-frame, such as the first symbol of thesub-frame, can be used for downlink control channel (PDCCH). PDCCHscarry dynamic allocated resources, such as physical resource blocks(PRBs) and modulation and coding scheme (MCS).

A transport channel transfers signaling and data between the L1 and MAClayers. A physical channel is mapped to a transport channel.

Downlink transport channel types include a broadcast channel (BCH), adownlink shared channel (DL-SCH), a paging channel (PCH) and a multicastchannel (MCH). The BCH is used for transmitting system information. TheDL-SCH supports HARQ, dynamic link adaptation by varying the modulation,coding and transmit power, and both dynamic and semi-static resourceallocation. The DL-SCH also may enable broadcast in the entire cell andthe use of beamforming. The PCH is used for paging the UE. The MCH isused for multicast or broadcast service transmission.

Uplink transport channel types include an uplink shared channel (UL-SCH)and random access channel(s) (RACH). The UL-SCH supports HARQ anddynamic link adaptation by varying the transmit power and potentiallymodulation and coding. The UL-SCH also may enable the use ofbeamforming. The RACH is normally used for initial access to a cell.

The MAC sublayer provides data transfer services on logical channels. Aset of logical channel types is defined for different data transferservices offered by MAC. Each logical channel type is defined accordingto the type of information transferred.

Logical channels are generally classified into two groups. The twogroups are control channels for the transfer of control planeinformation and traffic channels for the transfer of user planeinformation.

Control channels are used for transfer of control plane informationonly. The control channels provided by MAC include a broadcast controlchannel (BCCH), a paging control channel (PCCH), a common controlchannel (CCCH), a multicast control channel (MCCH) and a dedicatedcontrol channel (DCCH). The BCCH is a downlink channel for broadcastingsystem control information. The PCCH is a downlink channel thattransfers paging information and is used when the network does not knowthe location cell of the UE. The CCCH is used by UEs having no RRCconnection with the network. The MCCH is a point-to-multipoint downlinkchannel used for transmitting MBMS control information from the networkto the UE. The DCCH is a point-to-point bi-directional channel used byUEs having an RRC connection that transmits dedicated controlinformation between the UE and the network.

Traffic channels are used for the transfer of user plane informationonly. The traffic channels provided by MAC include a dedicated trafficchannel (DTCH) and a multicast traffic channel (MTCH). The DTCH is apoint-to-point channel, dedicated to one UE for the transfer of userinformation and can exist in both uplink and downlink. The MTCH is apoint-to-multipoint downlink channel for transmitting traffic data fromthe network to the UE.

Uplink connections between logical channels and transport channelsinclude a DCCH that can be mapped to the UL-SCH, a DTCH that can bemapped to the UL-SCH and a CCCH that can be mapped to the UL-SCH.Downlink connections between logical channels and transport channelsinclude a BCCH that can be mapped to the BCH or the DL-SCH, a PCCH thatcan be mapped to the PCH, a DCCH that can be mapped to the DL-SCH, and aDTCH that can be mapped to the DL-SCH, a MCCH that can be mapped to theMCH, and a MTCH that can be mapped to the MCH.

A home eNB (HeNB) is described. It may be referred to Section 4.6 of3GPP TS 36.300 V10.5.0 (2011-09).

The E-UTRAN architecture may deploy a HeNB gateway (HeNB GW) to allowthe S1 interface between the HeNB and the EPC to support a large numberof HeNBs in a scalable manner. The HeNB GW serves as a concentrator forthe control plane (C-Plane), specifically the S1-MME interface. The S1-Uinterface from the HeNB may be terminated at the HeNB GW, or a directlogical user plane (U-Plane) connection between the HeNB and the S-GWmay be used.

The S1 interface is defined as the interface:

-   -   Between the HeNB GW and the core network,    -   Between the HeNB and the HeNB GW,    -   Between the HeNB and the core network,    -   Between the eNB and the core network.

The HeNB GW appears to the MME as an eNB. The HeNB GW appears to theHeNB as an MME. The S1 interface between the HeNB and the EPC is thesame, regardless whether the HeNB is connected to the EPC via the HeNBGW or not.

The HeNB GW shall connect to the EPC in a way that inbound and outboundmobility to cells served by the HeNB GW shall not necessarily requireinter MME handovers. One HeNB serves only one cell.

The functions supported by the HeNB shall be the same as those supportedby the eNB (with possible exceptions, e.g., NAS node selection function(NNSF)) and the procedures run between the HeNB and the EPC shall be thesame as those between the eNB and the EPC (with possible exceptions,e.g., S5 procedures in case of local IP access (LIPA) support).

FIG. 5 shows overall E-UTRAN architecture with deployed HeNB GW.

Referring to FIG. 5, the E-UTRAN includes eNBs 50, HeNBs 60 and HeNB GW69. One or more E-UTRAN MME/S-GW 59 may be positioned at the end of thenetwork and connected to an external network. The eNBs 50 are connectedto each other through the X2 interface. The eNBs 50 are connected to theMME/S-GW 59 through the S1 interface. The HeNB GW 69 is connected to theMME/S-GW 59 through the S1 interface. The HeNBs 60 are connected to theHeNB GW 69 through the S1 interface or are connected to the MME/S-GW 59through the S1 interface or S5 interface.

Referring to FIG. 5, the HeNBs 60 are connected to each other throughthe X2 interface. Only the HeNBs with the same closed subscriber group(CSG) identifiers (IDs) may have the direct X2 interface even if someHeNBs may support a hybrid mode. If specific conditions are satisfied,handover may be done through direct X2 interface. That is, X2-basedhandover between HeNBs may be allowed if no access control at the MME isneeded, i.e., when the handover is between closed/hybrid access HeNBshaving the same CSG IDs or when the target HeNB is an open access HeNB.

Moreover, the X2 interface between a HeNB and macro eNB have beendiscussed for X2 handover between the HeNB and macro eNB. A direct X2interface or an indirect X2 interface between the HeNB and macro eNB maybe set up.

A transport network layer (TNL) address discovery is described. If theeNB is aware of the eNB ID of the candidate eNB (e.g., via the automaticneighbor relation (ANR) function) but not a TNL address suitable forstream control transmission protocol (SCTP) connectivity, then the eNBcan utilize the configuration transfer function to determine the TNLaddress as follows:

-   -   The eNB sends the eNB configuration transfer message to the MME        to request the TNL address of the candidate eNB, and includes        relevant information such as the source and target eNB ID.    -   The MME relays the request by sending the MME configuration        transfer message to the candidate eNB identified by the target        eNB ID.    -   The candidate eNB responds by sending the eNB configuration        transfer message containing one or more TNL addresses to be used        for SCTP connectivity with the initiating eNB, and includes        other relevant information such as the source and target eNB ID.    -   The MME relays the response by sending the MME configuration        transfer message to the initiating eNB identified by the target        eNB ID.

For the efficient X2 setup procedure between the HeNB and macro eNB, theTNL address discovery procedure may need to be defined clearly.

SUMMARY OF INVENTION Technical Problem

The present invention provides a method for transmitting an indicationin a wireless communication system. The present invention provides amethod for transmitting an indication of actual X2 setup in a wirelesscommunication system. The present invention provides a method forperforming a transport network layer (TNL) address discovery procedurewhen an X2-gateway (GW) exists.

Solution to Problem

In an aspect, a method for transmitting, by a macro eNodeB (eNB), anindication in a wireless communication system is provided. The methodincludes transmitting an indication of X2 setup to a mobility managemententity (MME). The indication of X2 setup indicates whether a direct X2interface between the macro eNB and a home eNB (HeNB) or an indirect X2interface going through an X2-gateway (GW) is to be set up. The methodfurther includes receiving a transport network layer (TNL) address and asource eNB identifier (ID) from the MME, wherein the TNL address and thesource eNB ID are determined by the HeNB according to the indication ofX2 setup.

The TNL address determined by the HeNB may be a TNL address of the HeNB,if the indication of X2 setup indicates that the direct X2 interfacebetween the macro eNB and the HeNB is to be set up. The source eNB IDmay be an ID of the HeNB.

The TNL address determined by the HeNB may be a TNL address of theX2-GW, if the indication of X2 setup indicates that the indirect X2interface going through the X2-GW is to be set up. The source eNB ID maybe one of an ID of the HeNB or an ID of the X2-GW.

The indication of X2 setup may be transmitted via an eNB configurationtransfer message, and the TNL address and the source eNB ID may bereceived via an MME configuration transfer message.

In another aspect, a method for transmitting, by a home eNodeB (HeNB), atransport network layer (TNL) address in a wireless communication systemis provided. The method includes receiving an indication of X2 setupfrom a HeNB gateway (HeNB GW). The indication of X2 setup indicateswhether a direct X2 interface between a macro eNB and the HeNB or anindirect X2 interface going through an X2-GW is to be set up. The methodfurther includes transmitting a TNL address and a source eNB identifier(ID) to the HeNB GW according to the indication of X2 setup.

In another aspect, a method for transmitting, by a first eNodeB (eNB), atransport network layer (TNL) address in a wireless communication systemis provided. The method includes transmitting at least one of a TNLaddress of the first eNB and a TNL address of an X2-gateway (GW), and asource eNB identifier (ID) upon receiving a mobility management entity(MME) configuration transfer message.

The method may further include determining the TNL address to betransmitted as only the TNL address of the X2-GW, or as both the TNLaddress of the first eNB and the TNL address of the X2-GW.

The source eNB ID may be determined as either one of an ID of the firsteNB or an ID of the X2-GW.

The method may further include transmitting an indication of X2 setupwhich indicates whether a direct X2 interface between the first eNB anda second eNB or an indirect X2 interface going through the X2-GW is tobe set up. The indication of X2 setup may be transmitted via an eNBconfiguration transfer message.

The at least one TNL address and source eNB ID may be transmitted via aneNB configuration transfer message.

The first eNB may be a macro eNB.

The first eNB may be a home eNB (HeNB).

Advantageous Effects of Invention

An X2 setup problem for a home eNodeB (HeNB) mobility enhancement, whichis caused by the existing of X2-GW, can be solved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows network structure of an evolved universal mobiletelecommunication system (E-UMTS).

FIG. 2 shows architecture of a typical E-UTRAN and a typical EPC.

FIG. 3 shows a user-plane protocol and a control-plane protocol stackfor an E-UMTS.

FIG. 4 shows a structure of a physical channel.

FIG. 5 shows overall E-UTRAN architecture with deployed HeNB GW.

FIG. 6 shows an example of an X2 interface setup between a macro eNB andHeNB.

FIG. 7 shows an example of a TNL address discovery procedure accordingto an embodiment of the present invention.

FIG. 8 shows another example of a TNL address discovery procedureaccording to an embodiment of the present invention.

FIG. 9 shows another example of a TNL address discovery procedureaccording to an embodiment of the present invention.

FIG. 10 shows another example of a TNL address discovery procedureaccording to an embodiment of the present invention.

FIG. 11 shows another example of a TNL address discovery procedureaccording to an embodiment of the present invention.

FIG. 12 shows another example of a TNL address discovery procedureaccording to an embodiment of the present invention.

FIG. 13 is a block diagram showing wireless communication system toimplement an embodiment of the present invention.

MODE FOR THE INVENTION

The technology described below can be used in various wirelesscommunication systems such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), etc. The CDMA canbe implemented with a radio technology such as universal terrestrialradio access (UTRA) or CDMA-2000. The TDMA can be implemented with aradio technology such as global system for mobile communications(GSM)/general packet ratio service (GPRS)/enhanced data rate for GSMevolution (EDGE). The OFDMA can be implemented with a radio technologysuch as institute of electrical and electronics engineers (IEEE) 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), etc.IEEE 802.16m is an evolution of IEEE 802.16e, and provides backwardcompatibility with an IEEE 802.16-based system. The UTRA is a part of auniversal mobile telecommunication system (UMTS). 3rd generationpartnership project (3GPP) long term evolution (LTE) is a part of anevolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses the OFDMA indownlink and uses the SC-FDMA in uplink. LTE-advance (LTE-A) is anevolution of the 3GPP LTE.

For clarity, the following description will focus on the LTE-A. However,technical features of the present invention are not limited thereto.

FIG. 6 shows an example of an X2 interface setup between a macro eNB andHeNB.

Referring to FIG. 6, the E-UTRAN includes macro eNBs 70, 71, 72, HeNBs80, 81, 82, 83, HeNB GW 89, and X2-GW 90. One or more E-UTRAN MME/S-GW79 may be positioned at the end of the network and connected to anexternal network. The macro eNBs 70 are connected to each other throughthe X2 interface. The macro eNBs 70, 71 are connected to the MME/S-GW 79through the S1 interface. The HeNB GW 89 is connected to the MME/S-GW 79through the S1 interface. The HeNB 81, 83 are connected to the HeNB GW89 through the S1 interface. The HeNB 82 is connected to the MME/S-GW 79through the S1 interface. The HeNBs 81, 82, 83 are connected to eachother through the X2 interface.

The X2-GW 90 is additionally deployed. The X2-GW 90 is connected to theHeNB1 81 through the X2 interface. However, connection between the X2-GW90 and HeNB3 83 is not established, yet. In addition, connection betweenthe macro eNB1 71 and X2-GW 90 or connection between the macro eNB1 71and HeNB3 83 is not established, yet.

The X2 interface may be introduced between the macro eNB and HeNB. Theremay exist two possible connections, one of which is to connect the HeNBand macro eNB indirectly by going through the X2-GW (path “A” in FIG.6). The other way is to connect the HeNB and macro eNB directly by theX2 interface (path “B” in FIG. 6). Based on the structure describedabove in FIG. 6, X2 handover may be performed more quickly between theHeNB and macro eNB.

In FIG. 6, the X2 interface is not yet set between the macro eNB1 71 andHeNB3 83, which means whether the direct X2 interface or indirect X2interface going through the X2-GW has not been set up. Depending on thesituation, at least one of the direct X2 interface or indirect X2interface may be setup, and accordingly, some problems may occur.

Firstly, there may exist a scenario that the macro eNB1 71 discoversanother HeNB3 83 through a UE ANR report from a HeNB3 cell. Uponreceiving the UE ANR report, the macro eNB1 71 would initiate TNLaddress discovery procedure in order to get the TNL address of the X2-GW90 or HeNB3 83, which is the necessary condition for X2 setup. Thus, themacro eNB1 71 would transmit an eNB configuration transfer message toits MME, which will forward the eNB configuration transfer message tothe HeNB GW 89 by using an MME configuration transfer message. In thetwo messages, the source and target eNB IDs are a macro eNB1 ID andHeNB3 ID, respectively. In the next step, the HeNB GW 89 would forwardthe MME configuration transfer message to the HeNB3 83. Then, the HeNB383 would reply back the proper TNL address to the HeNB GW 89 by usingthe eNB configuration transfer message.

From the point of view of the macro eNB1 71, the macro eNB1 71 knowsthat X2 setup will be done whether between the macro eNB1 71 and X2-GW90, i.e., indirectly, or between the macro eNB1 71 and HeNB3 83, i.e.,directly. However, the HeNB3 83 doesn't know it. That is, the HeNB3 83cannot know whether the direct X2 interface or indirect X2 interfacewould be set up, and the HeNB3 83 needs to know whether the TNL addressof itself or the TNL address of the X2-GW 90 should be replied back tothe macro eNB1 71. Also, the source ID in the eNB configuration transfermessage/MME configuration transfer message should be decided dependingon whether the indirect X2 interface between the X2-GW 90 and macro eNB171 or the direct X2 interface between the HeNB3 83 and macro eNB 71 isset.

Secondly, there may exist another scenario that the HeNB3 83 discoversthe macro eNB1 71 through a UE ANR report from a macro eNB1 cell. Uponreceiving the UE ANR report, the HeNB3 83 would initiate TNL addressdiscovery procedure in order to get the TNL address of the macro eNB171, which is the necessary condition for X2 setup. Similar problemdescribed above may occur since the macro eNB1 71 cannot know whetherthe direct X2 interface or indirect X2 interface would be set up.

Thirdly, it is possible that the direct X2 setup is not allowed. Thus,only the X2 setup going through the X2-GW 90 is available. In thisscenario, some problem still may occur due to the existing of X2-GW 90.

To solve the problem describe above, it is important to notify the HeNB3that the actual X2 setup is whether between the macro eNB and HeNB orbetween the macro eNB and the corresponding X2-GW. Also, for the thirdscenario, the behavior of the HeNB3 needs to be defined clearly. Thus,the following key ideas may be proposed in order to make sure that theTNL address discovery procedure works well when the X2-GW exists.

FIG. 7 shows an example of a TNL address discovery procedure accordingto an embodiment of the present invention. This example corresponds to ascenario in which a UE at a macro eNB1 cell discovers a HeNB3.

1) When the macro eNB initiates the TNL address discovery proceduretowards the HeNB which supports CSG (open mode, hybrid mode or closedmode), the macro eNB includes an indication of the actual X2 setupbetween the macro eNB and HeNB or between the macro eNB and thecorresponding X2-GW in an eNB configuration transfer message to thecorresponding MME. That is, the indication of actual X2 setup indicateswhich X2 interface, i.e., direct or indirect, would be set up. The macroeNB transmits the eNB configuration transfer message including theindication of the actual X2 setup to the MME.

2) The MME forwards the indication of actual X2 setup between the macroeNB and HeNB or between the macro eNB and the corresponding X2-GWthrough an MME configuration transfer message to the corresponding HeNBGW.

3) The HeNB GW forwards the indication of actual X2 setup between themacro eNB and HeNB or between the macro eNB and the corresponding X2-GWthrough the MME configuration transfer message to the correspondingHeNB.

4) Upon receiving the indication of actual X2 setup, the HeNB3 decides aTNL address and source eNB ID. The TNL address may be either one of aTNL address of the HeNB3 or a TNL address of the X2-GW according to theactual X2 setup. The source eNB ID may also be either one of an eNB IDof the HeNB3 or an eNB ID of the X2-GW according to the actual X2 setup.More specifically, if the indication of actual X2 setup indicates X2setup between the X2-GW and macro eNB, i.e., the indirect X2 interface,the HeNB3 uses the TNL address of the X2-GW and the source eNB ID may bethe eNB ID of the HeNB3 or the eNB ID of the X2-GW. If the indicationindicates X2 setup between the HeNB3 and macro eNB, i.e., the direct X2interface, the HeNB3 uses the TNL address of the HeNB3 and the eNB ID ofthe HeNB3. The HeNB3 may reply to the HeNB GW/MME using the eNBconfiguration transfer message including the TNL address and the sourceeNB ID.

5) After receiving the TNL address from the HeNB3, the macro eNB1 mayinitiate the X2 setup procedure.

FIG. 8 shows another example of a TNL address discovery procedureaccording to an embodiment of the present invention. FIG. 8 shows aflowchart corresponding to the embodiment of the present inventiondescribed in FIG. 7.

At step S100, the macro eNB1 finds new neighbor HeNB3. It is assumedthat an ID of the macro eNB1 is 1, and a tracking area identity (TAI) ofthe macro eNB1 is 1. It is also assumed that an ID of the HeNB3 is 3,and a TAI of the HeNB3 is 2.

At step S110, the macro eNB1 transmits an eNB configuration transfermessage to the MME. The eNB configuration transfer message includes theeNB ID of the macro eNB1/HeNB3, the TAI of the macro eNB1/HeNB3, and aself-optimization network (SON) information request. The eNBconfiguration transfer message also includes an indication of actual X2setup. The indication of actual X2 setup indicates which X2 interface,i.e., direct or indirect, would be set up.

At step S120, the MME forwards the indication of actual X2 setup to theHeNB GW by transmitting an MME configuration transfer message to theHeNB GW. At step S130, the HeNB GW forwards the indication of actual X2setup to the HeNB3 by transmitting the MME configuration transfermessage to the HeNB GW. The MME configuration transfer message includesthe eNB ID of the macro eNB1/HeNB3, the TAI of the macro eNB1/HeNB3, andSON information request.

At step S140, upon receiving the indication actual X2 setup, the HeNB3determines a TNL address and source eNB ID. If the indication actual X2setup indicates the X2s setup between the macro eNB1 and the X2-GW, theHeNB3 uses the TNL address of the X2-GW and the source eNB ID may be theeNB ID of the HeNB3 or the eNB ID of the X2-GW. If the indication actualX2 setup indicates the X2 setup between the macro eNB1 and the HeNB3,the HeNB3 uses the TNL address of the HeNB3 and the eNB ID of the HeNB3.

At step S150, the HeNB3 transmits the eNB configuration transfer messageto the HeNB GW. The eNB configuration transfer message includes the TNLaddress and the source eNB ID determined by the HeNB3.

At step S160, the HeNB forwards the TNL address and the source eNB ID tothe MME by transmitting the eNB configuration transfer message to theMME. At step S170, the MME forwards the TNL address and the source eNBID to the macro eNB1 by transmitting the MME configuration transfermessage to the macro eNB1.

At step S180, the macro eNB1 and HeNB GW exchanges an X2 setuprequest/response message. At step S190, the HeNB GW and HeNB3 exchangesthe X2 setup request/response message.

FIG. 9 shows another example of a TNL address discovery procedureaccording to an embodiment of the present invention. This examplecorresponds to a scenario in which a UE at a HeNB3 cell discovers amacro eNB1. It is assumed that the TNL address of the X2 GW ispre-configured to the macro eNB1.

1) When the HeNB3 initiates the TNL address discovery procedure towardsthe macro eNB, the HeNB3 initiates the TNL address discovery procedureby using an eNB configuration transfer message to the corresponding HeNBGW.

2) The HeNB GW forwards the eNB configuration transfer message to theMME.

3) The MME then forwards it to the macro eNB1 by using an MMEconfiguration transfer message.

4) Upon receiving the MME configuration transfer message, the macro eNB1decides a TNL address and source eNB ID when it replies to the MME byusing the eNB configuration transfer message. The TNL address may be aTNL address of the X2-GW since it is pre-configured at the macro eNB1.In this case, the source ID may be an ID of the X2-GW or macro eNB1 ID.Or, the TNL address may be a TNL address of the macro eNB1. In thiscase, the source ID may be an ID of the X2-GW or macro eNB1 ID. Themacro eNB1 may reply to the MME using the eNB configuration transfermessage including the TNL address and the source eNB ID.

Additionally, the macro eNB may also include an indication of actual X2setup explicitly in the eNB configuration transfer message. Accordingly,upon receiving the indication of actual X2 setup, the HeNB can knowwhere to setup the X2 interface, i.e., indirectly with the X2-GW ordirectly with the macro eNB1.

FIG. 10 shows another example of a TNL address discovery procedureaccording to an embodiment of the present invention. FIG. 10 shows aflowchart corresponding to the embodiment of the present inventiondescribed in FIG. 9.

At step S200, the HeNB3 finds new neighbor macro eNB1. It is assumedthat an ID of the HeNB3 is 3, and a TAI of the HeNB3 is 2. It is alsoassumed that an ID of the macro eNB1 is 1, and a TAI of the macro eNB1is 1.

At step S210, the HeNB3 transmits an eNB configuration transfer messageto the HeNB GW. The eNB configuration transfer message includes the eNBID of the HeNB3/macro eNB1, the TAI of the HeNB3/macro eNB1, and a SONinformation request. At step S220, the HeNB GW forwards the eNBconfiguration transfer message to the MME. At step S230, the MMEforwards the eNB configuration transfer message to the macro eNB1 bytransmitting an MME configuration transfer message to the macro eNB1.

At step S240, upon receiving the MME configuration transfer message, themacro eNB1 determines a TNL address and source eNB ID. The TNL addressmay be determined as either one of a TNL address of the macro eNB1 or aTNL address of the X2-GW. The TNL address of the macro eNB1 correspondsto the direct X2 interface between the HeNB3 and macro eNB1. The TNLaddress of the X2-GW corresponds to the indirect X2 interface betweenthe HeNB3 and macro eNB1 going through the X2-GW. Also, the source eNBID may be determined as either one of the macro eNB1 ID or an ID of theX2-GW.

At step S250, the macro eNB1 transmits the eNB configuration transfermessage to the MME. The eNB configuration transfer message includes theTNL address and the source eNB ID determined by the macro eNB1. Also,the eNB configuration transfer message may include an indication ofactual X2 setup. The indication of actual X2 setup indicates which X2interface, i.e., direct or indirect, would be set up according to theTNL address determined by the macro eNB1.

At step S260, the MME forwards the TNL address and the source eNB ID tothe HeNB GW by transmitting the MME configuration transfer message tothe HeNB GW. At step S270, the HeNB GW forwards the TNL address and thesource eNB ID to the HeNB3 by transmitting the MME configurationtransfer message to the HeNB3.

FIG. 11 shows another example of a TNL address discovery procedureaccording to an embodiment of the present invention. This examplecorresponds to a scenario in which a UE at a macro eNB1 cell discovers aHeNB3. This example is as similar as the example described in FIG. 10except that the macro eNB1 initiates the TNL address discoveryprocedure. It is assumed that the TNL address of the X2 GW ispreconfigured to the HeNB3.

At step S300, the macro eNB1 finds new neighbor HeNB3. It is assumedthat an ID of the macro eNB1 is 1, and a TAI of the macro eNB1 is 1. Itis also assumed that an ID of the HeNB3 is 3, and a TAI of the HeNB3 is2.

At step S310, the macro eNB1 transmits an eNB configuration transfermessage to the MME. The eNB configuration transfer message includes theeNB ID of the macro eNB1/HeNB3, the TAI of the macro eNB1/HeNB3, and aSON information request. At step S320, the MME forwards the eNBconfiguration transfer message to the HeNB GW by transmitting the MMEconfiguration transfer message. At step S330, the HeNB GW forwards theMME configuration transfer message to the HeNB3.

At step S340, upon receiving the MME configuration transfer message, theHeNB3 determines a TNL address and source eNB ID. The TNL address may bedetermined as only the TNL address of the X2-GW, or as both the TNLaddress of the first eNB and the TNL address of the X2-GW. The TNLaddress of the HeNB3 corresponds to the direct X2 interface between theHeNB3 and macro eNB1. The TNL address of the X2-GW corresponds to theindirect X2 interface between the HeNB3 and macro eNB1 going through theX2-GW. Also, the source eNB ID may be determined as either one of theHeNB3 ID or an ID of the X2-GW.

At step S350, the HeNB3 transmits the eNB configuration transfer messageto the HeNB GW. The eNB configuration transfer message includes the TNLaddress and the source eNB ID determined by the HeNB3. Also, the eNBconfiguration transfer message may include an indication of actual X2setup. The indication of actual X2 setup indicates which X2 interface,i.e., direct or indirect, would be set up according to the TNL addressdetermined by the HeNB3. Or, the indication of actual X2 setup may beimplicitly expressed by the TNL address of the X2-GW.

At step S360, the HeNB GW forwards the TNL address and the source eNB IDto the MME by transmitting the eNB configuration transfer message to theMME. At step S370, the MME forwards the TNL address and the source eNBID to the macro eNB1 by transmitting the MME configuration transfermessage to the macro eNB1.

FIG. 12 shows another example of a TNL address discovery procedureaccording to an embodiment of the present invention. This examplecorresponds to a scenario in which only the indirect X2 interface goingthrough the X2-GW is possible.

At step S400, the macro eNB1 finds new neighbor HeNB3. It is assumedthat an ID of the macro eNB1 is 1, and a TAI of the macro eNB1 is 1. Itis also assumed that an ID of the HeNB3 is 3, and a TAI of the HeNB3 is2.

At step S410, the macro eNB1 transmits an eNB configuration transfermessage to the MME. The eNB configuration transfer message includes theeNB ID of the macro eNB1/HeNB3, the TAI of the macro eNB1/HeNB3, and aSON information request. The eNB configuration transfer message may alsoinclude an indication of actual X2 setup. The indication of actual X2setup indicates that the indirect X2 interface between the macro eNB1and X2-GW would be set up.

At step S420, the MME transmits an MME configuration transfer message tothe HeNB GW. At step S430, the HeNB GW transmits the MME configurationtransfer message to the HeNB GW. The MME configuration transfer messageincludes the eNB ID of the macro eNB1/HeNB3, the TAI of the macroeNB1/HeNB3, and SON information request. The MME configuration transfermessage may also include the indication of actual X2 setup.

At step S440, in this case, since only the indirect X2 interface wouldbe setup, the HeNB3 does not need to determine a TNL address and sourceeNB ID. The HeNB3 uses the TNL address of the X2-GW and the source eNBID may be the eNB ID of the HeNB3 or the eNB ID of the X2-GW.

At step S450, the HeNB3 transmits the eNB configuration transfer messageto the HeNB GW. The eNB configuration transfer message includes the TNLaddress and the source eNB ID determined by the HeNB3.

At step S460, the HeNB forwards the TNL address and the source eNB ID tothe MME by transmitting the eNB configuration transfer message to theMME. At step S470, the MME forwards the TNL address and the source eNBID to the macro eNB1 by transmitting the MME configuration transfermessage to the macro eNB1.

At step S480, the macro eNB1 and HeNB GW exchanges an X2 setuprequest/response message. At step S490, the HeNB GW and HeNB3 exchangesthe X2 setup request/response message.

FIG. 13 is a block diagram showing wireless communication system toimplement an embodiment of the present invention.

An eNB/HeNB 800 includes a processor 810, a memory 820, and an RF (radiofrequency) unit 830. The processor 810 may be configured to implementproposed functions, procedures, and/or methods in this description.Layers of the radio interface protocol may be implemented in theprocessor 810. The memory 820 is operatively coupled with the processor810 and stores a variety of information to operate the processor 810.The RF unit 830 is operatively coupled with the processor 810, andtransmits and/or receives a radio signal.

An MME/HeNB GW 900 may include a processor 910, a memory 920 and a RFunit 930. The processor 910 may be configured to implement proposedfunctions, procedures and/or methods described in this description.Layers of the radio interface protocol may be implemented in theprocessor 910. The memory 920 is operatively coupled with the processor910 and stores a variety of information to operate the processor 910.The RF unit 930 is operatively coupled with the processor 910, andtransmits and/or receives a radio signal.

The processors 810, 910 may include application-specific integratedcircuit (ASIC), other chipset, logic circuit and/or data processingdevice. The memories 820, 920 may include read-only memory (ROM), randomaccess memory (RAM), flash memory, memory card, storage medium and/orother storage device. The RF units 830, 930 may include basebandcircuitry to process radio frequency signals. When the embodiments areimplemented in software, the techniques described herein can beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The modules can be stored inmemories 820, 920 and executed by processors 810, 910. The memories 820,920 can be implemented within the processors 810, 910 or external to theprocessors 810, 910 in which case those can be communicatively coupledto the processors 810, 910 via various means as is known in the art.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope and spirit of the present disclosure.

1.-15. (canceled)
 16. A method for transmitting, by a first eNodeB(eNB), a transport network layer (TNL) address in a wirelesscommunication system, the method comprising: receiving an indication ofan indirect X2 interface between the first eNB and a second eNB, whichgoes through an X2 gateway (X2-GW); and transmitting a TNL address ofthe X2-GW based on the indication of the indirect X2 interface towardsthe second eNB.
 17. The method of claim 16, wherein the indication ofthe indirect X2 interface is received via a mobility management entity(MME) configuration transfer message.
 18. The method of claim 16,wherein the TNL address of the X2-GW is transmitted via an eNBconfiguration transfer message.
 19. The method of claim 16, wherein atleast one of the first eNB or the second eNB is a home eNB.
 20. Themethod of claim 16, wherein the indication of the indirect X2 interfacecorresponds to the TNL address of the X2-GW.